Recently, as fiber has been prominent as a core material in various industrial fields such as a space field, an aircraft field, a shipping industry, building materials, sport goods, and the like, as well as clothing, a demand for high performance fiber capable of being stronger than general fiber for clothes such as nylon, polyester, and enduring high temperature has been increased.
As the high performance fiber, there are carbon fiber, aramid fiber, and the like. The carbon fiber indicates a filament made of non-graphitic carbon obtained by performing of stabilization, carbonation, and stretching graphitization at 250° C. or more on organic fiber or precursor fiber prepared by spinning an organic material such as a resin, a pitch, or the like. The carbon fiber has advantages such as high elastic modulus, high strength, low coefficient of thermal expansion, and high electric and thermal conductivity, but there is still a problem in long-term reliability due to a micropore formation possibility during a preparation process, or the like.
In addition, since the aramid fiber, which is fiber developed by Dupont in the 1970s, has strength of at least two times the strength of the existing fiber, and has a relatively high elongation at break (3˜4%) as compared to the carbon fiber having an excellent anti-creping property as well as strength and elastic modulus, the aramid fiber has advantages such as an excellent flexural fatigue property and an impact absorption property, but the aramid fiber is not strong against acid as known from the fact that a strong acid such as sulfuric acid, or the like, is used as a spinning solvent. Therefore, at the time of exposure to outdoor ultraviolet light for a long time, durability of the aramid fiber is not good as compared to general fiber such as polyester fiber, and dyeability may be deteriorated. In addition, since an moisture absorption rate is relatively high (4 to 6%), and in the case in which the aramid fiber is left at a high temperature for a long time, dynamic performance thereof may be deteriorated by hydrolysis, the aramid fiber is disadvantageous for long term preservation and usage.
Further, polyimide containing a monomer substituted by a nitrile group has been disclosed in Korean Patent Application No. 1994-5840 and Korean Patent No. 0171994, but the polyamide is not spun at a high draw ratio, at the time of spinning the polyamide, breakage is frequently generated even at a low draw ratio, and mechanical properties should be further improved. Therefore, practically, it is difficult to commercially use the polyamide.
Therefore, research into a technology of diversifying a fiber product by improving fatigue properties or increasing strength of fiber, or the like, eco-friendly fiber having excellent dyeability or an excellent crimping property, and a preparation method thereof have been continuously conducted.